Laser module

ABSTRACT

First block ( 10 ) includes internal flow path ( 15 ). A cooling medium flows inside internal flow path ( 15 ). Curved part ( 56 ) is provided at a corner between bottom surface ( 54 ) and side wall surface ( 55 ) of internal flow path ( 15 ). Curved part ( 56 ) is continuously connected to bottom surface ( 54 ) and side wall surface ( 55 ) of internal flow path ( 15 ) and has a curved shape.

This application is a continuation application of the PCT InternationalApplication No. PCT/JP2021/028263 filed on Jul. 30, 2021, which claimthe benefit of foreign priority of Japanese patent application No.2020-138549 filed on Aug. 19, 2020, the contents all of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a laser module.

BACKGROUND ART

Conventionally, a water-cooled radiator used for cooling a heatingelement such as a laser element is known (see, e.g., PTL 1).

PTL 1 discloses a configuration in which an upper heat radiation plate,an intermediate heat radiation plate, and a lower heat radiation plateare laminated in three layers, and cooling water flows in a folded waterpassage formed between a water inlet and a water outlet in acommunication hole of the intermediate heat radiation plate to cool aheat receiving end of the intermediate heat radiation plate.

Here, the heat radiation plate is made of a metal material havingexcellent heat conduction, for example, copper (Cu). In addition,plating layers are provided on the surface of the base material in orderto enhance corrosion resistance of the heat radiation plate.

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2005-294769

SUMMARY OF THE INVENTION Technical Problems

However, in a configuration in which a water passage is formed in a heatradiation plate as in a conventional water-cooled radiator, a crack maybe generated in plating layers provided in a base material, water maypenetrate from the crack, ionization of copper may be facilitated byapplication of a current, and the base material may corrode.

Specifically, in the process of plating the heat radiation plate, theplating layer growing in the direction orthogonal to the bottom surfaceof the water passage and the plating layer growing in the directionorthogonal to the side wall surface of the water passage overlap eachother at a corner between the bottom surface and the side wall surfaceof the water passage, and grain boundaries are generated in the platinglayers. As a result, a crack is likely to be generated in the platinglayers at the corner between the bottom surface and the side wallsurface of the water passage.

In addition, when heat generated at the laser element is transferred tothe heat radiation plate and thermal stress is applied to the heatradiation plate, the stress is concentrated toward the corner betweenthe bottom surface and the side wall surface of the water passage, and acrack is likely to be generated in the plating layers.

The present disclosure has been made in view of such a point, and anobject of the disclosure is to suppress corrosion of a block for coolinga laser element.

Solutions to Problems

A first aspect of the present invention is a laser module including: alaser element configured to emit laser light; a first block including amounting surface, the laser element being placed on the mountingsurface; a second block stacked on a stacking surface of the firstblock, the stacking surface being opposite to the mounting surface ofthe first block, in which the first block includes a recess, the recessbeing a part of the stacking surface and allowing a cooling medium toflow inside the recess, the recess includes a bottom surface, a sidewall surface, and a curved part at a corner between the bottom surfaceand the side wall surface of the recess, and the curved part iscontinuously connected to the bottom surface and the side wall surfaceand has a curved shape.

According to the first aspect of the present invention, the recess isprovided in the first block. A cooling medium to flow inside the recess.A curved part is provided at a corner between the bottom surface and theside wall surface of the recess. The curved part is continuouslyconnected to the bottom surface and the side wall surface of the recessand has a curved shape.

With such a configuration, corrosion of the first block for cooling thelaser element can be suppressed.

Specifically, the base material of the first block is provided withplating layers for enhancing corrosion resistance. Here, when the cornerbetween the bottom surface and the side wall surface of the recess isformed at a right angle, grain boundaries are generated in the platinglayers at the corner between the bottom surface and the side wallsurface of the recess in the process of plating the first block, and acrack is likely to be generated in the plating layers.

On the other hand, in the present disclosure, the corner between thebottom surface and the side wall surface of the recess is formed in acurved shape. Thus, the plating layers growing in respective directionsorthogonal to the bottom surface, the curved surface, and the side wallsurface of the recess are continuously connected to each other, andgrain boundaries are less likely to be generated in the plating layers.

In addition, when heat generated at the laser element is transferred tothe first block and thermal stress is applied to the first block, thestress toward the corner between the bottom surface and the side wallsurface of the recess is dispersed at the curved part. As a result, acrack is less likely to be generated in the plating layers provided atthe corner of the recess, and corrosion of the first block can besuppressed.

In a second aspect of the present invention according to the firstaspect of the present invention, the first block includes: a basematerial including a first metal; an alloy layer including an alloycontaining the first metal and a second metal different from the firstmetal, the alloy layer provided on a surface of the base material; and afirst plating layer including the second metal and provided on a surfaceof the alloy layer.

In the second aspect of the present invention, the first block includesa base material, an alloy layer provided on a surface of the basematerial, and a first plating layer provided on a surface of the alloylayer. The base material is made of a first metal. The first platinglayer is made of a second metal. The alloy layer is made of an alloycontaining the first metal and the second metal. For example, when thebase material is made of copper (Cu) and the first plating layer is madeof nickel (Ni), the alloy layer is made of an alloy of copper andnickel.

By providing the alloy layer between the base material and the firstplating layer in this manner, the adhesion of the first plating layer isimproved. Additionally, the alloy layer is formed by, for example,performing sinter treatment. Therefore, even when there is a flaw on thesurface of the base material, the flaw is filled and planarized when thealloy layer is formed. As a result, the growth characteristics of thefirst plating layer becomes excellent, and generation of a crack can besuppressed.

In a third aspect of the present invention according to the secondaspect of the present invention, the first plating layer is providedwith, on a surface of the first plating layer, a second plating layerhaving corrosion resistance higher than corrosion resistance of thefirst plating layer.

In the third aspect of the present invention, the second plating layeris provided on the surface of the first plating layer. The secondplating layer is made of metal having corrosion resistance higher thanthat of the first plating layer. For example, when the first platinglayer is made of nickel (Ni), the second plating layer only needs to bemade of gold (Au).

In this manner, corrosion resistance of the first block can be improved,and corrosion of the first block can be suppressed.

In a fourth aspect of the present invention according to any one of thefirst to third aspects of the present invention, the first blockincludes a plurality of fins each standing upright from the bottomsurface of the recess and disposed spaced from each other in the recess,the first block includes a curved part at a corner between the bottomsurface of the recess and each of the plurality of fins, and the curvedpart is continuously connected to the bottom surface and each of theplurality of fins and has a curved shape.

In the fourth aspect of the present invention, the first block includesa plurality of fins each standing upright from the bottom surface of therecess.

A curved part is provided at a corner between the bottom surface of therecess and the fin. The curved part is continuously connected to thebottom surface of the recess and the fin and has a curved shape.

As described above, by providing the plurality of fins in the firstblock to increase the heat dissipation area, heat generated at the laserelement can be efficiently dissipated from the plurality of fins.

Furthermore, the corner between the bottom surface of the recess and thefin is formed in a curved shape. Thus, the plating layers growing inrespective directions orthogonal to the bottom surface of the recess,the curved surface, and the side wall surface of the fin arecontinuously connected to each other, and grain boundaries are lesslikely to be generated in the plating layers.

In addition, when heat generated at the laser element is transferred tothe first block and thermal stress is applied to the first block, thestress toward the corner between the bottom surface of the recess andthe side wall surface of the fin is dispersed at the curved part. As aresult, a crack is less likely to be generated in the plating layersprovided at the corner of the recess, and corrosion of the first blockcan be suppressed.

Advantageous Effect of Invention

According to the present disclosure, corrosion of the block for coolingthe laser element can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a configuration of a lasermodule according to an exemplary embodiment.

FIG. 2 is an exploded perspective view illustrating the configuration ofthe laser module.

FIG. 3 is a perspective view illustrating a configuration of a firstblock on an stacking surface side.

FIG. 4 is a view when the first block is viewed from the stackingsurface side.

FIG. 5 is a front cross-sectional view illustrating a configuration of acurved part and plating layers of the first block in a partiallyenlarged manner.

FIG. 6 is a plan cross-sectional view illustrating the configuration ofthe laser module.

FIG. 7 is a front cross-sectional view illustrating the configuration ofthe laser module.

FIG. 8 is a side cross-sectional view illustrating the configuration ofthe laser module.

DESCRIPTION OF EMBODIMENT

Hereinafter, exemplary embodiments of the present disclosure will bedescribed with reference to the drawings. The following description ofpreferable exemplary embodiments is merely illustrative in nature, andis not intended to limit the present disclosure, its application, or itsuse.

As illustrated in FIGS. 1 and 2 , laser module 1 includes first block10, second block 20, third block 30, laser element 40, and insulatinglayer 45.

First block 10 has conductivity. As will be described in detail later,first block 10 is mainly made of copper (Cu). In first block 10, nickel(Ni) and gold (Au) are sequentially plated on a block made of copper.

First block 10 includes mounting surface 11. Mounting surface 11 isformed by recessing a part of an upper surface of first block 10.Mounting surface 11 is provided at an end, in an emission direction oflaser light L (a direction indicated by an arrow line in FIG. 1 ), ofthe upper surface of first block 10.

Laser element 40 is mounted on mounting surface 11 via conductivesub-mount 41. Sub-mount 41 is mainly made of a copper-tungsten alloy(CuW).

Laser element 40 includes a lower surface as a positive electrode and anupper surface as a negative electrode. In laser element 40, when acurrent flows from the positive electrode toward the negative electrode,laser light L is output from a light emission surface.

The light emission surface of laser element 40 substantially coincideswith a front end of mounting surface 11 of first block 10. The positiveelectrode of laser element 40 is electrically connected to first block10. First block 10 has a function as an electrode block electricallyconnected to the positive electrode of laser element 40.

Insulating layer 45 is provided on the upper surface of first block 10.Insulating layer 45 is made of polyimide, ceramic, or the like.

Second block 20 is overlapped on a side opposite to mounting surface 11of first block 10. Second block 20 is mainly made of stainless steel(SUS). In second block 20, nickel (Ni) and gold (Au) are sequentiallyplated on a block made of stainless steel.

As will be described in detail later, internal flow path 15 throughwhich a cooling medium to flow is provided between first block 10 andsecond block 20 (see FIG. 8 ).

Third block 30 has conductivity. Third block 30 is mainly made of copper(Cu). In third block 30, nickel (Ni) and gold (Au) are sequentiallyplated on a block made of copper.

Third block 30 is provided on laser element 40 and insulating layer 45.Third block 30 is electrically connected to laser element 40 via a bump(not illustrated). Third block 30 has a function as an electrode blockelectrically connected to the negative electrode of laser element 40.

First block 10, second block 20, and third block 30 are fastened byscrews (not illustrated). At this time, third block 30 is fastened tofirst block 10 and second block 20 in an electrically insulated state.

In thus configured laser module 1, when a current flows from thepositive electrode to the negative electrode of laser element 40, laserlight L is output from the light emission surface on the side of laserelement 40. At this time, heat generated in laser element 40 istransmitted to first block 10, second block 20, and third block 30.

As illustrated in FIGS. 3 and 4 , first block 10 is provided withinternal flow path 15 (recess). Internal flow path 15 is formed byrecessing a part of a lower surface of first block 10. Internal flowpath 15 extends rearward (leftward in FIG. 8 ) from a surface on a sideopposite to mounting surface 11.

First block 10 is provided with a plurality of fins 12. Fins 12 eachstand upright from the surface on the side opposite to mounting surface11 of first block 10. Fins 12 are formed in a plate shape and extendalong the emission direction of laser light L. The plurality of fins 12are disposed spaced from each other in internal flow path 15 in athickness direction.

In this manner, by providing the plurality of fins 12 in first block 10,a heat dissipation area of first block 10 is increased.

Incidentally, plating layers for enhancing corrosion resistance areprovided on the surface of the base material of first block 10. Here,when a corner between the bottom surface and the side wall surface ofinternal flow path 15 or a corner between the bottom surface of internalflow path 15 and the side surface of fin 12 is formed at a right angle,a crack may be generated in the plating layers, and water may penetratefrom the crack, so that the base material may corrode.

Therefore, laser module 1 according to the present exemplary embodimenthas a structure in which a crack is less likely to be generated in theplating layers of first block 10 and corrosion of the first block issuppressed.

Specifically, as illustrated in FIG. 5 , first block 10 includes basematerial 50, alloy layer 51, first plating layer 52, and second platinglayer 53. Alloy layer 51 is provided on the surface of base material 50.First plating layer 52 is provided on the surface of alloy layer 51.Second plating layer 53 is provided on the surface of first platinglayer 52.

Base material 50 is made of a first metal. The first metal is, forexample, copper (Cu). Curved part 56 is provided at a corner betweenbottom surface 54 and side wall surface 55 of internal flow path 15 inbase material 50. Curved part 56 is continuously connected to bottomsurface 54 and side wall surface 55 of internal flow path 15 and has acurved shape.

Similarly, curved part 56 is provided at a corner between bottom surface54 of internal flow path 15 and the side surface of fin 12 in basematerial 50. Curved part 56 is continuously connected to bottom surface54 of internal flow path 15 and the side surface of fin 12 and has acurved shape.

Curved part 56 is formed by processing a corner of internal flow path 15to be in a round shape having a radius within a range from about 0.1 mmto about 3.0 mm inclusive, for example.

Alloy layer 51 is provided on the surface of base material 50. Alloylayer 51 is made of an alloy containing the first metal and the secondmetal different from the first metal. In the present exemplaryembodiment, the first metal is copper (Cu), and the second metal isnickel (Ni).

Alloy layer 51 is formed by plating base material 50 with nickel as thesecond metal and then performing sinter treatment at a temperaturewithin a range, for example, from 700° C. to 900° C. inclusive,preferably at 800° C.

The thickness of alloy layer 51 is set within a range, for example, from1 μm to 3 μm inclusive, preferably to 2 μm. Therefore, the thickness ofthe plating layer before the sinter treatment is preferably set to about4 μm. With this configuration, even when there is a flaw on the surfaceof base material 50, the flaw is filled and planarized when alloy layer51 is formed.

First plating layer 52 is provided on the surface of alloy layer 51.First plating layer 52 is made of nickel as the second metal. Thethickness of first plating layer 52 is set within a range, for example,from 3 μm to 6 μm inclusive, preferably to 3.5 μm. With thisconfiguration, generation of pinholes in first plating layer 52 can besuppressed.

In addition, first plating layer 52 is formed on the surface of alloylayer 51 containing nickel. Thus, the growth characteristics of firstplating layer 52 becomes excellent, and the adhesion of first platinglayer 52 is improved.

Second plating layer 53 is provided on the surface of first platinglayer 52. Second plating layer 53 is made of metal having corrosionresistance higher than that of first plating layer 52. For example, whenfirst plating layer 52 is made of nickel, second plating layer 53 ismade of gold (Au).

The thickness of second plating layer 53 is set within a range, forexample, from 0.1 μm to 1.0 μm inclusive, preferably to 0.3 μm. In thismanner, corrosion resistance of first block 10 can be improved, andcorrosion of first block 10 can be suppressed.

By providing curved part 56 at the corner between bottom surface 54 andside wall surface 55 of internal flow path 15 as described above, theplating layers growing in respective directions orthogonal to bottomsurface 54, curved part 56, and side wall surface 55 of internal flowpath 15 are continuously connected to each other in the process ofplating treatment. As a result, grain boundaries are less likely to begenerated in the plating layers. The same applies to the corner betweenbottom surface 54 of internal flow path 15 and the side surface of fin12.

In addition, when heat generated at laser element 40 is transferred tofirst block 10 and thermal stress is applied to first block 10, thestress toward the corner of internal flow path 15 is dispersed at curvedpart 56.

As a result, a crack is less likely to be generated in alloy layer 51,first plating layer 52, and second plating layer 53 provided at thecorner of internal flow path 15.

Further, corrosion of first block 10 due to the cooling medium flowingthrough internal flow path 15 can be suppressed.

As illustrated in FIGS. 6 to 8 , second block 20 is overlapped on theside opposite to mounting surface 11 of first block 10. Internal flowpath 15 is provided between first block 10 and second block 20.

Second block 20 includes a plurality of supply holes 21 and dischargehole 22. The plurality of supply holes 21 are open between the pluralityof fins 12 when viewed from an stacking direction of first block 10 andsecond block 20. A cooling medium is supplied from the outside to supplyhole 21 by a chiller unit (not illustrated). The cooling medium is, forexample, water. Supply holes 21 supply the cooling medium to internalflow path 15. In FIGS. 6 to 8 , the flow of the cooling medium isindicated by arrow lines.

The cooling medium supplied from the plurality of supply holes 21 tointernal flow path 15 is supplied between the plurality of fins 12 andflows toward a downstream side along an upper surface of internal flowpath 15.

Discharge hole 22 is open on the downstream side of internal flow path15 in second block 20. Discharge hole 22 discharges the cooling mediumfrom internal flow path 15 to the outside to return the cooling mediumto the chiller unit (not illustrated).

Discharge hole 22 extends in a direction inclined with respect to thestacking direction of first block 10 and second block 20. In the exampleillustrated in FIG. 8 , discharge hole 22 is inclined obliquely downwardtoward the left side. Discharge hole 22 may be inclined by, for example,45° with respect to the stacking direction.

First block 10 includes guide part 16. Guide part 16 guides the coolingmedium flowing through internal flow path 15 toward an opening positionof discharge hole 22. Guide part 16 is configured by a side wall on thedownstream side of internal flow path 15. Guide part 16 extends in adirection forming an obtuse angle with respect to the surface on theside opposite to mounting surface 11. Guide part 16 may extend in adirection perpendicular to the surface on the side opposite to mountingsurface 11.

This enables the cooling medium having flowed through internal flow path15 and having collided with guide part 16 to be smoothly guided fromguide part 16 toward discharge hole 22.

Here, discharge hole 22 is inclined with respect to the stackingdirection. Thus, the cooling medium flowing toward discharge hole 22collides with an inner peripheral surface of discharge hole 22 and thenflows while being distributed to an upstream side and a downstream sideof discharge hole 22 along the inclination direction of discharge hole22. The inclination of discharge hole 22 is provided to generate such aflow of the cooling medium.

Meanwhile, a negative pressure is generated around supply hole 21 due tothe flow during supplying the cooling medium from supply hole 21.Therefore, the cooling medium flowing toward the upstream side ofdischarge hole 22 passes between the plurality of fins 12, returns to anopening position of supply hole 21, and circulates through internal flowpath 15.

The cooling medium supplied from supply hole 21 flows along the surfaceon the side opposite to mounting surface 11 of first block 10 to cool abase end side of fin 12.

Meanwhile, the cooling medium returning from discharge hole 22 flowsalong an upper surface of second block 20 and cools a front end of fin12.

As a result, by circulating the cooling medium along the entire surfaceof fins 12, heat generated at laser element 40 can be efficientlydissipated from the plurality of fins 12.

INDUSTRIAL APPLICABILITY

As described above, since the present disclosure can provide a highpractical effect that corrosion of a block for cooling a laser elementcan be suppressed, the present disclosure is extremely useful and hashigh industrial applicability.

REFERENCE MARKS IN THE DRAWINGS

-   1 laser module-   10 first block-   11 mounting surface-   12 fin-   15 internal flow path (recess)-   20 second block-   40 laser element-   50 base material-   51 alloy layer-   52 first plating layer-   53 second plating layer-   54 bottom surface-   55 side wall surface-   56 curved part-   L laser light

1. A laser module comprising: a laser element configured to emit laserlight; a first block including a mounting surface, the laser elementbeing placed on the mounting surface; and a second block stacked on astacking surface of the first block, the stacking surface being oppositeto the mounting surface of the first block, wherein the first blockincludes a recess, the recess being a part of the stacking surface andallowing a cooling medium to flow inside the recess, and the recessincludes a bottom surface, a side wall surface, and a curved part at acorner between the bottom surface and the side wall surface of therecess, and the curved part is continuously connected to the bottomsurface and the side wall surface and has a curved shape.
 2. The lasermodule according to claim 1, wherein the first block includes a basematerial including a first metal, an alloy layer including an alloycontaining the first metal and a second metal different from the firstmetal, the alloy layer provided on a surface of the base material, and afirst plating layer including the second metal and provided on a surfaceof the alloy layer.
 3. The laser module according to claim 2, whereinthe first plating layer is provided with, on a surface of the firstplating layer, a second plating layer having corrosion resistance higherthan corrosion resistance of the first plating layer.
 4. The lasermodule according to claim 1, wherein the first block includes aplurality of fins each standing upright from the bottom surface of therecess and disposed spaced from each other in the recess, and the firstblock includes a curved part at a corner between the bottom surface ofthe recess and each of the plurality of fins, and the curved part iscontinuously connected to the bottom surface and each of the pluralityof fins and has a curved shape.